Adult ileo-ileal intussusception caused by inflammatory fibroid polyp leading to small bowel obstruction: a case report with comprehensive literature review

Abstract Ileo-ileal intussusception, an infrequent cause of small bowel obstruction in adults, can be initiated by inflammatory fibroid polyps. These are uncommon, benign submucosal lesions of the gastrointestinal tract. This case report explores an adult patient with inflammatory fibroid polyps-induced ileo-ileal intussusception.


Introduction
Intussusception occurs when a segment of intestine (intussusceptum) telescopes into the adjacent segment (intussuscipiens) along with its mesenteric fold [1].This telescoping, also known as invagination, can arise from various causes.In the small bowel, benign growths like lipomas and leiomyomas are frequent culprits.Inf lammatory fibroid polyps (IFPs), while less common, can also be a cause.Conversely, malignant lesions are more often implicated in large intestine intussusception [2].Notably, IFPs are typically benign submucosal tumors residing in the stomach, although they can occur throughout the gastrointestinal tract [3,4].
This case report presents a rare occurrence of ileo-ileal intussusception triggered by an IFP in a 35-year-old woman with intestinal obstruction symptoms.A combination of CT scan, intraoperative findings, and histopathological analysis established the final diagnosis, excluding other possibilities.

Case report
A 35-year-old woman presented to the emergency department with a 3-day history of lower abdominal pain, constipation, and a 2-day fever.She also reported six episodes of vomiting.Notably, she was able to pass f lattus.The patient denied any prior episodes of similar symptoms or any significant past surgical or medical history.Her vitals including pulse and blood pressure were within normal limits.There were no physical signs of dehydration.Examination revealed localized tenderness on deep palpation at hypogastrium, however, there was no rebound tenderness.Her basic blood work up including complete blood count, renal and liver function tests were within normal limits.
The patient was shifted to the radiology department for screening ultrasonography which revealed dilated small bowel loops with to-and-fro peristalsis with maximum caliber of 3.5 mm.With provisional diagnosis of intestinal obstruction, patient was planned for CT scan to localize the transition point.CT scan (Fig. 1) demonstrated telescoping of one of the pelvic ileal loops into adjacent ileal loop for a length of ∼14 cm.The distal bowel segment receiving the prolapsing bowel segment showed circumferential mural thickening measuring approximately 7 mm with resultant dilatation of the proximal jejunal, and mid ileal pelvic loops which showed air f luid levels measuring upto 3.6 cm in maximum caliber.The distal bowel loops beyond this point appeared collapsed.Thus, a diagnosis of ileo-ileal intussuception was established.
The patient was informed about the diagnosis and the need for surgery.Surgical resection of the intussuscepted segment was performed, followed by anastomosis of the adjacent ileal segments.There were no complications during surgery or the immediate postoperative period.Oral f luids were gradually introduced after 3 days, followed by a transition to solid foods after 5 days.The patient made a good recovery.A follow-up appointment 2 weeks later confirmed good healing of the surgical incision.
The gross examination of the resected specimen revealed a 15 × 4 cm segment of intestine containing a submucosal polypoid lesion measuring 2 × 2 × 1 cm, located 4 cm from one end and 10 cm from the other (Fig. 2).No lymph nodes were identified in the specimen.Microscopic examination (Fig. 3) demonstrated a submucosal tumor composed of spindle-shaped cells within a loose fibromyxoid background.There was an infiltrate of inf lammatory cells, predominantly eosinophils, and variably sized blood vessels.Based on these findings, the diagnosis was suggestive of an inf lammatory fibroid polyp.Importantly, the proximal and distal resection margins were free of tumor involvement.

Discussion
Intussusception arises when a segment of intestine telescopes into the adjacent lumen, along with its associated mesentery.The precise etiology remains elusive, although theories suggest that intraluminal irritants disrupt normal peristalsis, triggering the process [2].Untreated intussusception can progress to ischemia, necrosis, and perforation [5,7,9,10].
Compared to pediatric cases, adult intussusception of the large bowel exhibits a stronger association with malignant etiologies.Primary neoplasms, including adenocarcinoma and lymphoma, are frequently implicated, alongside secondary involvement from metastatic disease.Additionally, carcinoids, leiomyosarcomas, and gastrointestinal stromal tumors can also contribute to this phenomenon [3-7, 9, 10].
Accurate diagnosis hinges on a meticulous medical history, thorough clinical examination, and a tailored selection of imaging modalities.These may include plain radiography, ultrasound, barium contrast studies, CT, and MRI.Plain abdominal X-ray often serves as the initial imaging tool, but typically reveals nonspecific air-f luid levels suggestive of obstruction [2,5,10].Sonographic characteristics include the appearance of a target or doughnut sign in the transverse view, and in longitudinal view, it may display a pseudo-kidney, sandwich, or hayfork sign [5,7,10].
CT surpasses ultrasound for intussusception diagnosis due to its unimpeded visualization by gas.It boasts high sensitivity (58%-100%) [1] and aids in evaluation of location and extent of the lesion or lead point proximity to surrounding structures and potential complications [3,6,7,10,14].CT scan effectively identifies ileo-ileal intussusception caused by benign polyps.These polyps appear as elongated, fat-containing, pedunculated filling defects within the proximal ileum [2,6,7,[14][15][16].Additionally, CT demonstrates characteristic findings of small bowel obstruction, including proximal bowel dilation and a transition point to the distal, collapsed segment.A hallmark sign on CT is the 'bulls-eye' or 'target' appearance in axial sections and the 'sausage-shaped' lesion in coronal sections, collectively known as the double-ring sign [ 2,6,[14][15][16].
MRI advancements, particularly the half-Fourier acquisition single-shot turbo spin-echo technique, are increasing diagnostic accuracy for bowel diseases, albeit with lower utilization compared to other modalities [1,17,18].This technique offers a characteristic 'bowel-within-bowel' or 'coiled-spring' appearance on imaging.Additionally, a combination of T2-weighted and diffusion sequences with contrast-enhanced T1-weighted imaging can facilitate polyp detection [1,17,18].
In pediatric intussusception, pneumatic reduction under f luoroscopy or hydrostatic reduction under ultrasound guidance reigns supreme due to its high success rate and minimal perforation risk.Conversely, surgical intervention (laparotomy or laparoscopy) remains the mainstay in adults.This is driven by the frequent presence of an underlying pathology, such as malignancy, requiring resection and histopathological confirmation [1,2,5,7,10,19].

Conclusion
Adult intussusception, a rare entity, often presents with acute intestinal obstruction.Prompt and accurate diagnosis is crucial to prevent complications like bowel infarction and perforation, and to facilitate resection of the underlying lead point, particularly when malignancy is a potential culprit.Imaging plays a pivotal role in guiding diagnosis and treatment for these patients.Therefore, a thorough understanding of both the clinical presentation and the characteristic imaging findings of intussusception is paramount for optimal management and minimizing potential complications.

Figure 1 .
Figure 1.Scannogram (A) showing dilated small bowel loops in central abdomen (black arrows).Axial (B), coronal (C) and sagittal (D, E) images of contrast CT showing telescoping of pelvic ileal loop (dotted white arrows) with upstream small bowel obstruction (solid white arrow).

Figure 3 .
Figure 3. Histopathological examination reveals spindle-shaped cells within a loose, fibromyxoid background.The infiltrate of inf lammatory cells, predominantly eosinophils and the presence of variably sized blood vessels are also evident.